Ultrasonic diagnostic apparatuses transmit and receive ultrasonic waves to and from a living body so as to obtain two-dimensional information on the inside of the living body, and these apparatuses are utilized in various medical fields. Such ultrasonic diagnostic apparatuses are provided with a probe for transmitting ultrasonic waves to the inside of a body of a subject and receiving reflected waves from a body tissue. Such an ultrasonic diagnostic apparatus provided with a probe as a component thereof is disclosed in, for example, Japanese Patent No. 1746663 or the like.
FIG. 5 is a schematic cross-sectional view showing an example of a probe as a component of a conventional ultrasonic diagnostic apparatus. This ultrasonic probe includes a sensor portion 200, a cable portion 201, and a connector portion 202 to be connected to a main body of the ultrasonic diagnostic apparatus (not shown).
The sensor portion 200 includes an ultrasonic element 203 for transmitting and receiving ultrasonic waves, a sensor signal substrate 204 and a sensor ground substrate 205 connected electrically with the ultrasonic element 203, an acoustic matching plate 220 and an acoustic lens 207 provided on an ultrasonic wave transmitting/receiving surface of the ultrasonic element 203, and a backing layer 206 provided on a back surface (surface opposite to the ultrasonic wave transmitting/receiving surface) of the ultrasonic element 203. The sensor portion 200 further includes a sensor connector 217 connected with the sensor signal substrate 204 and the sensor ground substrate 205.
The cable portion 201 includes a plurality of signal wires 209, each including a signal line 209a and a ground line 209b, a cable substrate 208 connected with the signal wires 209, and a cable connector 218 connected with the cable substrate 208. In the cable portion 201, an outer periphery of the signal wires 209 is covered with a cable shield 210 and further is protected by a sheath 211. A shielding plate 219, which is a film formed of an insulating layer 219b and a conductive layer 219a formed on a surface of the insulating layer 219b, is arranged so as to surround the cable substrate 208 and the cable connector 218 as well as a part of an outer periphery of the sensor portion 200, and is connected with the cable shield 210.
The connector portion 202 includes a connector 215 for connecting with the main body and pins 216, each being connected with the signal line 209a or the ground line 209b. These components are accommodated in a connector housing 213. The connector housing 213 is provided with a conductive layer 214 on its inner wall surface. The cable shield 210 is connected with the conductive layer 214 and is to be connected with a frame ground or a signal ground of the main body of the ultrasonic diagnostic apparatus when the probe is connected with the main body of the ultrasonic diagnostic apparatus.
However, in the above conventional example, a ground electrode of the ultrasonic element 203 is connected with the ground line 209b through the sensor ground substrate 205, the sensor connector 217 as well as the cable connector 218, and the cable substrate 208. Accordingly, due to limitations on the number of connector poles and the like, it is difficult to secure a sufficient number of poles for a ground. When a sufficient number of poles are not secured for a ground, resistance between the sensor ground substrate and the cable substrate increases, and in the case where a noise current flows through the ground due to exposure to an electromagnetic environment, the ground potential varies, and image noise may be caused.